A system and method for treating contaminated water are provided. The system can include one or more collecting basins for collecting water, such as rain water, runoff water, etc. The system can further include one or more containment basins, one or more polishing basins, and a pumping system for moving water through the system. The containment basins and polishing basins can utilize techniques for reducing a contaminant concentration in the water. The system can further include a source for adding process water to the system and combining it with the collected water to form a system water in order to reduce a contaminant concentration in the system water and accommodate higher volumes of collected water and/or higher pollutant concentrations therein. The system can also include an ultraviolet emitting device and/or a heating device for reducing the level of living bacteria in the system water.